OUTLINE: This is a randomized, double-blind, placebo-controlled, multicenter study. Patients are stratified according to prior ribavirin exposure for this infection (24 hours or more vs less than 24 hours) and requirement for ventilator support (yes vs no). Patients are randomized to one of two treatment arms. Arm I: Patients receive aerosolized ribavirin via face mask or oxygen tent over 2 hours 3 times daily or over 16-18 hours on days 1-10 and palivizumab IV 2 hours before ribavirin administration on day 1. Arm II: Patients receive aerosolized ribavirin as in arm I and placebo IV 2 hours before ribavirin administration on day 1. Patients are followed at 14, 21, and 28 days.